Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.78	7.650%	$189.2272	$189.23	$189.25	$189.20
Purchase #2	$189.70	3.721%	$196.7587	$196.76	$196.75	$196.80
Purchase #3	$88.82	13.140%	$100.4909	$100.49	$100.50	$100.50
Purchase #4	$114.46	13.784%	$130.2372	$130.24	$130.25	$130.20
Purchase #5	$183.25	7.127%	$196.3102	$196.31	$196.30	$196.30
Purchase #6	$180.38	4.248%	$188.0425	$188.04	$188.05	$188.00
Purchase #7	$62.30	7.551%	$67.0043	$67.00	$67.00	$67.00
7 purchase totals =	$994.69		$1,068.0710	$1,068.07	$1,068.10	$1,068.00